Here is an interesting article - which I somehow missed - that appeared in Mission Critical Communications some time ago. I checked my records and found I was traveling at that time (so I guess I can be excused).
In 2013, the Telecommunications Industry Association released ANSI/TIA-4950. This standard defines the requirements for Battery-Powered, Portable Land Mobile Radio Applications in Class I, II, and III, Division 1, Hazardous (Classified) Locations.
ANSI/TIA-4950 was developed to provide a standalone set of intrinsic safety requirements that address issues unique to two way radio equipment used in both classified and non-classified environments. These requirements however do not impede the traditional levels of RF performance in two-way radio systems.
Certification for ANSI/TIA-4950 is carried out by UL. UL has been involved in hazardous locations certification testing since 1930. They are a well established testing house with a proven track record and expertise in all area classifications, protection methods and product categories.
The Telecommunications Industry Association represents manufacturers and suppliers of global communications networks through standards development, policy and advocacy, business opportunities, market intelligence, and events and networking. TIA is accredited by the American National Standards Institute (ANSI). More information about ANSI/TIA-4950 can be found here.